Sewing machine convertible from lock stitch to chain stitch

ABSTRACT

A lock stitch sewing machine concurrently capable of carrying out chain stitching, namely, performing lock stitching when fitted with a throat plate adapted for said stitching and chain stitching when provided with another throat plate suitable for said stitching.

1 1 July 11,1972

United States Patent Yamashita [56] References Cited UNITED STATESPATENTS [$4] SEWING MACHINE CONVERTIBLE FROM LOCK STITCH T0 CHAIN STITCH[72] inventor:

Clriimo Yamashita, Aichi-ken, Japan [73] Assignee: Brother KogyoKahushikl Katha, Nagoyashi, Japan [22] Filed: May 19, 1970 PrimaryExaminer-James R. Boier Attorney-Kemon, Palmer & Eatabrook 211 App].No.2 311,734

[30] Foreign Application Priority Data ABSTRACT machine concurrentlycapable of carrying namely, performing lock stitching when ate adaptedfor said stitching and chain stitching when provided with another throatplate suitable for Feb. 26,1970

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P'ATENTEDJUL 1 I 1912 sum 10 or 11 INVENTOR.

PATENTCDJUU 1 I972 SHEET 11 0F 11 INVENTOR.

SEWING MACHINE CONVERTIBLE FROM LOCK STITCH 'IO CHAIN STITCH Thisinvention relates to a sewing machine for lock stitching and moreparticularly to a machine also capable of chain stitching.

A sewing machine in common use is of a lock stitch type. It has beendesired that the machine be also capable of forming chain stitches, ifrequired. To meet this demand, there have been employed various types ofchain stitch forming device. To convert the original lock stitch sewingmachine to that of chain stitching, however, the bobbin case or itsretainer of a rotary or oscillating type loop taker had to be replacedwith parts adapted for chain stitching. A lock stitch throat plate hadto be replaced with a different throat plate suited for chain stitchingwhich had a long needle aperture extending in the direction in whichthere was fed a work fabric. Further the needle thread had to be passedthrough an auxiliary thread guide in order to reduce the quantity of theneedle thread at the time of chain stitching. Thus replacement oroperation of a large number of parts caused great trouble to a generalhousehold user of a sewing machine. Moreover, parts were likely to belost and wrong operation led to the failure of chain stitching to besmoothly performed.

It is an object of the present invention to simplify the operation ofswitching from the lock stitching to the chain stitching or vice versaonly by replacement of a first and second throat plate adapted for lockand chain stitching respectively.

A further object of the invention is to reduce the quantity of theneedle thread released by a thread takeup mechanism when the secondthroat plate is fitted due to replacement and assure the smoothoperation of a chain stitching device, thereby effecting the betterperformance of chain stitching.

The present invention provides a sewing machine equipped with a lockstitching device as well as with a chain stitching device co-operabletherewith which is capable of lock stitching when fitted with a firstthroat plate adapted for said lock stitching and also chain stitchingwhen fitted with a second throat plate suited therefor, thereby enablingswitching from the lock to the chain stitching or vice versa to berealized simply by interchange of the first and second throat plates andoffering great convenience to a general household user of a sewingmachine.

Further, the present invention provides an easy operable sewing machineof simple construction which eliminates the necessity of replacingbobbins as has been required for the prior art sewing machine withoutcausing any trouble to a general user of a sewing machine and yet iscapable of being manufactured with ease and at low cost and alwaysperforming good chain stitching.

The present invention will be more fully understood from the followingdescription taken with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of an ordinary lock stitch sewing machinepermitting the use of a chain stitching device according to anembodiment of the present invention;

FIG. 2 is a similar perspective view of FIG. 1 showing by a twodots-dash line a frame containing a loop taker rotatable about ahorizontal axis parallel with the direction in which there is fed a workfabric;

FIG. 3 is an elevation of an entire chain stitching device where athread loop released from a loop taker is retained by a loop retainingmember;

FIG. 4 is a sectional view on line 4-4 of die chain stitching device ofFIG. 3;

FIG. 5 is a plan view of the device of FIG. 3, taken from line $-5thereof;

FIG. 6 is a sectional view on line 66 of the device of FIG.

FIG. 7 is a sectional view on line 7--7 of the device of FIG. 5;

FIG. 8 is a sectional view on line 88 of the device of FIG.

FIG. 9 is a sectional view on line 9-9 of the device of FIG.

FIG. 10 is a bottom plan view of the device of FIG. 7;

FIG. 11 is a perspective view of a first throat plate for lockstitching;

FIG. 12 is a perspective view of a second throat plate for chainstitching;

FIG. 13 is a bottom plan view of the second throat plate of FIG. I2;

FIG. 14 illustrates the condition in which there is pulled off the loopshown on line 14-14 of FIG. 4 in fragrnental en- Iargement;

FIG. 14a is a top view ofthe same;

FIG. 15 is a fragmental sectional view corresponding to FIG. 3 where thefirst throat plate is fitted to the frame;

FIG. 16 is a fragmental sectional view corresponding to FIG. 4 where theloop seized by the loop retaining member is released by the needle whenit is brought down;

FIG. 17 corresponds to FIG. 3 where the thread loop seized by the looptaker is being broadened;

FIG. 18 is a side view of the device of FIG. 17; FIG. I9 is an elevationof the thread seizing member of FIG. 1

, FIG. 20 illustrates the condition in which the thread seizing memberis brought to an operative position;

FIG. 21 shows the thread seizing member in an inoperative state; and

FIGS. 22 and 23 represent modifications of the thread seizing member,and FIG. 22 is an elevation thereof corresponding to FIG. ISI and FIG.23 corresponds to FIG. 20.

There will now be described with reference to the appended drawings achain stitching device according to an embodiment of the presentinvention.

The sewing machine of FIGS. 1 and 2 is an ordinary lock stitch type. Amachine frame 20 has a cylindrical bed 22 with a work supporting surfacemounted on a base 21. From the cylindrical bed 22 rises a standard 23supporting a bracket arm 24 overhanging the bed 22. At the end of thecylindrical bed 22 is positioned the later described loop taker. To saidend is movably fitted a cap member 25 so as to allow a bobbin case to beinserted into and taken out of the loop taker. A main drive shafl 26joumaled lengthwise in the bracket arm 24 drives all the moving parts ofthe sewing machine and may be actuated by an electric motor, by a foottreadle or the like (not shown). A counterbalanced crank 27 on the mainshaft 26 is operatively connected by means of a connecting rod 28 to aneedle bar 29 endwise slidable along a support 30 pivotally secured at31 on the bracket arm 24 and supporting at the bottom end a threadcarrying eyed needle 32. A needle thread takeup lever 33 is alsoactuated by the crank 27 and constrained by an anchor link 34 so as totighten and slacken the needle thread alternately in timed relationshipwith the endwise reciprocation of the needle 32. The path of the needlethread extends from a supply source (not shown) to a thread stretchingdevice 35 through an eyelet 36 in the takeup lever 33, and then throughappropriate guides such as a thread guide 37 on the needle bar 29 andfinally to the needle eye. Such arrangement for controlling the needlethread is typical of that which is required for lock stitching.

Numeral 38 is a loop taker shaft mounted on the frame 20 rotatably abouta horizontal axis parallel with the direction in which there is fed awork fabric 39. The loop taker shaft 38 is fitted at the end with a looptaker 41 carrying a loop seizing beak 40. The loop taker shaft 38 isconnected to a lower shaft 44 through a set of gears 42 and 43. Thelower shaft 44 interlooks with the main drive shaft 26 through a timingbelt 45, allowing die loop taker 41 to rotate twice for eachreciprocation of the needle. The needle and loop taker are driven insuch timed relationship that while the needle is brought down, the loopcoming out of the needle eye is seized by the loop taker 41 and whilethe needle is lifted, the seized loop is released from the loop taker41. To the loop taker 41 is fitted a bobbincase retainer 47 adapted toaccommodate an ordinary bobbin case 46. At the front upper part of theloop retainer 47 is formed a recess 48 near the point through which theneedle passes endwise. Numeral 49 represents a restraining member whosebase end is fixed to the frame by screws 50. At the end of therestraining member 49 is formed a tongue 53 freely engaging the recess48 so as to define an opening 52 therewith for permitting the passage ofthe released loop 51 released from the loop taker 41 pulled up by thethread takeup mechanism, thereby preventing the bobbin case retainer 47from rotating with the loop taker 41.

In the cylindrical bed 22 is disposed the later described feed dog 54perfonning the known four feed motions through the slot of the throatplate. The feed dot 54 advances the work fabric 39 on the work supportin a prescribed direction during each endwise reciprocation of theneedle 32. The feed dog 54 is fixed to a feed bar 56 connected to a feedadvancing shaft 55. The feed advancing shaft 55 is made to swing by atwoforked rod 58 embracing a feed cam 57 on the main shaft 26, causingthe feed dog 54 to make feed advancing and backward movements. The feedbar 56 is operatively connected to an oscillating shaft 61 actuated by arod 60 embracing a feed lift eccentric 59 fixed to the main shafi 26.Rotation of the main shaft 26 raises the feed dog 54. lt will beappreciated that as it is conventional in the art, a mechanism forlinearly feeding the work fabric 39 has a timed relationship to thereciprocation of the needle, so that while the needle 32 is lifted abovethe work fabric 39 on the throat plate, the feed dog 54 is lifted andadvanced and while the needle descends, the feed dog 54 is broughtbeneath the throat plate back to its original position. Numeral 62denotes an operating knob for causing the feed dog to make a drop feed.Numeral 63 is a manually operable knob for controlling the feed rate andreverse movement of the feed dog 54. Numeral 64 also denotes a manuallyoperable knob for controlling the amplitude of the zigzag motion of theneedle 32.

Numeral 65 is a loop retaining member having its intermediate portionrotatably mounted on the restraining member 49 by a stepped screw 66.The free end of the loop retaining member 65 constitutes a loopretaining section 67 for temporarily holding the released loop 51 pulledup through the opening 52 by the thread takeup mechanism. One side 67aof the loop retaining section 67 is so formed (FIG. 14) as not toproject from one side 53a of the tongue 53 positioned on that part ofthe restraining member 49 to which there is pressed the recess 48 of thebobbin case with the rotation of the loop taker 41. Accordingly, theloop 51 released from the loop taker 41 is pulled up without beingdetained in a space between said one side 53a of the tongue 53 andrecess 52. This enables good uniform chain stitches to be always formedwithout any ob struction and the loosening and consequential doubleformation of chain stitches.

Numeral 68 is a spring stretched across the other end of the loopretaining member 65 and the lug 70 of the later described fitting member69. The spring 68 causes the loop retaining member 65 to rotateanticlockwise as shown in P16. 5, thereby normally keeping the retainingsection 67 at a loop retaining position above the opening 52 so as tohold a loop released from the loop taker 41. Numeral 71 represents agroove formed at the upper part of the bobbin case retainer 47 acrossthe recess 48 so as to extend toward both sides thereof The groove 71has a sufliciently large size to receive the retaining section 67 of theloop retaining member 65. Above the groove 71 is disposed a projectingwall 72 for guiding the loop 51 released from the loop taker 41 onto theretaining section 67 so as to securely hold it thereon. The projectingwall 72 is so formed as to have its top positioned below that part ofthe bobbin case retainer 47 embracing both sides of the tongue 53 of therestraining member through which the needle 32 passes endwise.Accordingly, the loop released from the retaining section 67 is pulledup by the loop takeup mechanism without any obstruction and theslackening a consequential double formation of chain stitches. Coupledwith the fact that one side 67a of the retaining section 67 is so fonnedas not to project from one side 53a of the tongue 53, the aforementionedarrangement enables the needle thread to be fed smoothly and inconsequence good chain stitches to be always formed. Accordingly, thedevice of the present invention is very useful, because there is no needfor any machining of parts in practical application.

As seen from FIG. 3, the free end of the loop retaining member 65 isbent to surround the restraining member 49 so as to form a bent section74 which contacts the underside of the restraining member 49 to preventit from being lifted. Accordingly, when the retaining section 67 of theloop retaining member 65 lifts the bobbin case retainer 47 through theprojecting wall 72, there is not applied any excess load to the raceportion between the bobbin case retainer 47 and loop taker 41. Thisprevents the obstructed rotation of the loop taker 41 and the occurrenceof noises and wear. Further, since the loop is securely retained by theloop retaining member 65, there can be efiected constant chainstitching.

Numeral 75 is an actuating plate pivoted to the restraining member 49rotatably about a pin 76 fixed to the base end of said restrainingmember 49. The other end of the loop retaining member 65 engages therising section 750 of said actuating plate 75 by the action of thespring 68, so that the free end 75b of the actuating plate 75 isnormally urged upward so as to face the underside of the feed dog 54.The actuating plate 75 is swung downward with the descent of the feeddog 54 to cause the loop retaining member 65 to rotate against theaction of the spring 68, thereby allowing the loop 51 retained by theloop retaining member 65 to be released by the thread takeup mechanismafter the needle passes through the loop 51 next time.

As apparent from FIGS. 7, 9 and 10, a pivoting member 77 which supportsthe pin 76 of the actuating plate 75 so as to allow said actuating plate75 to rotate in a space between the backside of the restraining member49 and said pivoting plate 77, is fixed to the backside of therestraining member 49 by a pair of screws 79 passing through long slots78 perforated in the fitting member 69 and restraining member 49. Whenthe screws 79 are loosened to cause the pivoting member 77 to slideslightly along the long slots 78, then the pin 76 about which theactuating plate 75 is pivoted can be adjusted in position, therebycontrolling the time at which the loop retaining member 65 is actuatedby the feed dog 54. Accordingly, the operating time of the loopretaining member 65 is always set at a position adapted for chainstitching. To the suspended strip 93 of the restraining member 49 ispivoted a manually operable lever 94 for disengaging the throat plate bya stepped screw 95. One end 96 of the lever 94 so extends as to face theunderside of that part of the throat plate where there is disposed anengaging elastic plate 87, and the other end of the lever 94 constitutesan operating knob 97. Numeral 98 represents a spring stretched acrossthe throat plate disengaging lever 94 and restraining member 49. Thespring 98 causes the lever 94 to rotate anticlockwise as shown in FIG.6. According to the foregoing embodiment, there are fitted to therestraining member 49 all the loop retaining member 65, acmating plate75 and throat plate disengaging lever 94, so that all these members maybe put together as single unit, offering great advantage in assemblingand manufacturing the subject device.

To the bracket arm 24 is pivoted a lever 99 rotatably about a fulcrum100. At one end of the lever 99 is formed a thread seizing member 101bent in the U-shape which cooperates with the thread takeup lever 33 inorder to reduce the quantity of the needle thread released by saidthread takeup lever 33. The thread seizing member 101 is located in aslot 1010 through which the thread takeup lever 33 passes and so formedas to embrace it. The thread seizing member 101 is normally kept in aninoperative position where it does not substantially reduce the quantityof the needle thread slackened by the thread takeup mechanism by meansof a spring 102 stretched across the lever 99 and bracket arm 24 (H6.21). The other end of the lever 99 is connected through a link 103 to anactuating lever 105 fitted to the cylindrical bed 22 by means of a pivot104. The open end of the actuating lever 105 so extends as to face theunderside of the first throat plate 80.

The second throat plate 90 is provided with an actuating projection 106to press the other end of the actuating lever 105. Therefore when thereis fitted the second throat plate 90 the actuating lever 105 isdepressed by the actuating projection 106, causing the lever 99 torotate about the fulcrum 100 with the descent of the link 103 and inconsequence bringing the thread seizing member 101 from its inoperativeposition to that where it reduces the quantity of the needle thread asshown in FIG. 20. It will be noted that the first throat plate 80 is notprovided with the actuating projection 106.

There will now be described the application of a chain stitching deviceaccording to the foregoing embodiment and the manner in which there isconducted chain stitching. FIGS. 3 to 6 show the condition in which theloop 51 released from the loop seizing beak 40 of the loop taker 41 ispulled up by the thread takeup mechanism and passes through the opening52 between the tongue 53 and recess 48 to be retained by the retainingsection 67 of the loop retaining member 65. At this time the feed dog 54is in a rising position and disengaged from the actuating plate 75. Thesecond throat plate 90 for chain stitching does not of course have ascrew 89 as is the case with the first throat plate, so that when thefeed dog 54 is brought down, the actuating plate 75 is in an inoperativeposition and the thread seizing section 101 is actuated by the actuatingprojection 106 of the second throat plate 90 to be brought to anoperative position as shown in FIG. 20. When the work fabric 39 iscarried forward one stitch pitch by the feed dog 54 and the needle 32descends again into the loop 51 as shown in FIG. 16, then the feed dog54 is brought downward and its underside engages the free end 75b of theactuating plate 75 to press said plate 75 downward for rotation.Accordingly, the rising section 750 of the actuating plate 75 actuatesthe other end of the loop retaining member 65 engaging said plate 75 torotate the loop retaining member 65 against the action of the spring andrelease the loop 51 held by the retaining section 67.

As operation goes on, a fresh loop 51 formed by the fall of the needle32 is seized by the loop seizing beak 40 of the loop taker 41 inpreparation for the following chain stitching cycle. As shown in FIGS.17 and 18, while the fresh loop 51 is being broadened by the loop taker41, the preceding loop is pulled into the work fabric 39 to form a chainstitch. At this time, the thread takeup lever 33 descends to slacken thethread. However, since the thread seizing member 101 is positioned abovethe lever 33 when it is brought down, the thread is taken up by thethread seizing section 101 as shown in FIG. 20, so that the quantity ofthe needle thread to be supplied next time is reduced by that portionthus taken up. When the chain stitch is actually formed, the quantity ofthe needle thread becomes insufficient by that portion thus reduced asthe loop is gradually broadened by the loop taker 41. Accordingly, thepart of the preceding loop corresponding to said insufficient portion ispulled backward, causing the loop to be properly drawn into the workfabric 39 with the resultant formation of good chain stitches. Laterwhen the feed dog 54 is lifted again, the loop retaining member 65 isbrought back to its original position and the retaining section 67 isinserted into the groove 71 to be brought again to a position to retainthe loop.

When, upon completion of desired chain stitching, it is desired to use asewing machine for its original loclt' stitching, the cap member 25 ofthe cylindrical bed 22 is first opened and then the knob 97 of themanually operable lever 94 for disengaging the throat plate is depressedwith the finger to cause the lever 94 to rotate against the action ofthe spring 98. Then the engaging elastic plate 87 of the second throatplate 90 is disengaged from the projection 86 by one end 96 of the lever94, causing the second throat plate to be forcibly pushed out. Aftersaid second throat plate is taken out, there is fitted instead thepreviously provided first throat plate 80 for the original lockstitching. When the first throat plate 80 is to be fitted, it is firstguided on to the stepped section 81 or a throat plate receiving seat ofthe cylindrical bed 22 and then the elastic plate 85 of said firstthroat plate 80 is pressed in for engagement with the underside of theperipheral portion of the opening for said plate so as to securely setit in place and that side of said plate 00 where there is disposed theengaging elastic plate 87 is pressed from above. Then the engagingelastic plate 87 registers with the projection 86, setting the firstthroat plate 80 in a prescribed place as shown in FIG. 15. At this timethe screw 89 of the first throat plate engages the actuating plate 75 topress it for rotation from the position indicated by a two-dots dashline to that of a solid line, thus preventing its operation regardlessof the movement of the feed dog 54. The loop retaining member 65 isoperated in the same manner as in chain stitching, and brought to aninoperative position, quite independently of the loop passing throughthe opening 52 between the tongue 53 and recess 48 as shown in FIG. 16.Since the first throat plate 80 is not provided with an actuatingprojection 106, the actuating lever 105 is left free and the lever 99 isactuated by a spring 102 and the thread seizing member 101 is brought toan inoperative position shown in FIG. 21. At this time, the threadseizing member 101 is positioned below the lower dead point of thethread takeup lever 33 as illustrated, so that the quantity of theneedle thread slackened by the thread takeup lever 33 is notsubstantially reduced. Therefore, when the shuttle thread is supplied tothe case 46 there can be started ordinary lock stitching. When it isdesired again to perform chain stitching, it is only required to fit thesecond throat plate in place of the first throat plate 80 in the samemanner as in their interchange.

With the device according of the foregoing embodiment, the descent ofthe feed dog 54 due to operation of the knob 62 depresses the actuatingplate 75 for rotation, bringing the loop retaining member 65 to aninoperative position. Accordingly, when there is conducted embroideringby lock stitching with the feed dog 54 depressed, there is no need toexchange the second throat plate 90 for the first throat plate 80, sothat if it is desired alter chain stitching to carry out embroidering bylock stitching, it is not necessary to exchange these throat plates, butsimply to operate the knob 62.

FIGS. 22 and 23 represent modifications of the thread seizing member101. According to these modifications, the end of the lever 99 is fittedby a screw 107 with a thread seizing member 108 consisting of wire bentinto a rectangular form. The thread is supplied from the stretchingdevice 35 through the thread seizing member 108 to the thread takeuplever 33. With these modifications, when the thread seizing member 108is in an operative position as shown in FIG. 23, the quantity of theneedle thread slackened by the thread takeup lever 33 is decreased as inthe aforementioned embodiment. When the thread seizing member is broughtfrom its operative position down to its inoperative position, the threadis substantially left free from the action of the thread seizing member108, and its quantity is not decreased. The thread seizing member 108can be adjusted in position by loosening the screw 107.

As mentioned above, the present invention provides a lock stitch sewingmachine equipped with a chain stitching device widely to broaden itsapplication, thus offering great advantage to its general user.

What is claimed is:

1. A sewing machine including a frame having a bed with a worksupporting surface,

a thread carrying eyed needle supported on the frame for endwisereciprocation,

a needle thread take-up mechanism mounted on the frame for alternatelytightening and loosening the needle thread in timed relationship withthe endwise reciprocation of the needle,

said bed having an opening formed with a throat plate receiving seatabout said opening,

a loop taker assembly mounted in the bed below the throat platereceiving seat and circularly moved for seizure of thread loops formedby the reciprocation of the needle to form lock stitches,

a mechanism for linearly feeding a work fabric including a feed dogmaking the known four motions to advance the work fabric in a prescribeddirection on the work supporting surface during each endwisereciprocation of the needle,

a movable loop retaining member positioned in the opening of the bed fortemporarily retaining the loop which is being pulled up by the threadtake-up mechanism following the release from the loop taker assembly,

an urging means connected to the loop retaining member for normallysetting the loop retaining member in a position to retain the loopreleased from the loop taker assembly, and

an actuating member provided between the loop retaining member, and thefeed dog and having a first portion operatively connected with the loopretaining member, a second portion disposed adjacent the opening of thebed and a third portion normally urged toward the lower end of the feeddog, 7

said actuating member being adapted to move the loop retaining memberagainst the action of the urging means by the downward movement of thefeed dog, thereby causing the loop retained by the loop retaining memberto be released therefrom after the needle passes through the loop in thenext downward movement, said second portion of said actuating memberbeing adapted to be engaged by an actuating means on the bottom of athroat plate to thereby hold the loop retaining member in the releasedposition for lock stitching.

2. A sewing machine according to claim 1 including a throat plate formedwith an actuating means on the underside thereof engaging the secondportion of the actuating member thereby disengaging the actuating memberfrom the feed dog and setting the loop retaining member in non-operablecondition.

3. A sewing machine according to claim 1 including a throat plate and athread quantity adjusting means, said thread quantity adjusting meansbeing provided for reducing the quantity of the needle thread slackenedby the thread take-up mechanism in co-operation therewith, said threadquantity adjusting means including an actuatable member adjacent saidopening in said bed, and an actuating projection formed on the undersideof said throat plate cooperating with said actuatable member forbringing the thread quantity adjusting means in an operable position soas to reduce the quantity of the needle thread.

4. A sewing machine according to claim 3 wherein said thread take-upmechanism includes a reciprocable thread take-up lever, and said threadquantity adjusting member is bent in U-shaped to pass the take-up levertherein.

5 A sewing machine according to claim 1 wherein said feeding mechanismincludes means for causing the feed dog to remain in its loweredposition and an operating knob for the same, thereby the loop retainingmember is brought in arresting condition not to retain the loop releasedfrom the loop taker assembly through the actuating member when theoperating knob is operated.

6. A sewing machine including a frame having a bed with a worksupporting surface,

a thread carrying eyed needle supported on the frame for endwisereciprocation,

a needle thread take-up mechanism mounted on the frame for alternatelytightening and loosening the needle thread in time relationship with theendwise reciprocation of the needle,

said bed having an opening formed with a throat plate receiving seatabout said opening,

a throat plate removably mounted on the throat plate receiving seatabout said opening to close the opening of the bed, and perforated witha needle aperture adapted for chain stitching,

a loop taker mounted in the bed below the throat plate and rotated aboutan axis for seizure of thread loops formed by the reciprocation of theneedle to form lock stitches, a bobbin case retainer journaled in theloop taker and adapted to accomodate an ordinary bobbin case therein,

a restraining member fixed in the bed below the throat plate forpreventing the bobbin case retainer from rotating with the loop taker,

a mechanism for linearly feeding a work fabric including a feed dogmaking the known four motions to advance the work fabric in apredetermined direction during each endwise reciprocation of the needle,

a loop retaining member rotatbly supported on the restraining member totemporarily retain the loop which is being pulled up by the threadtake-up mechanism following the release from the loop taker at one ofits end,

spring means stretched between the loop retaining member and therestraining member for imparting a'rotating force to the loop retainingmember to normally keep it in a position to retain the loop releasedfrom the loop taker,

an actuating plate having a base end swingably supported by the restrainmember, an intermediate portion disposed adjacent the opening of the bedand a free end normally urged toward the lower end of the feed dog bythe engagement of the other end of the loop retaining member to which arotating force is imparted by the spring means,

said actuating plate being adapted to swing downward by the downwardmovement of the feed dog to rotate the loop retaining member against theaction of the spring means, thereby causing the loop retained by theloop retaining memberto be released therefrom after the needle passesthrough the loop in the next downward movement.

7. A sewing machine according to claim 6 wherein the restrainingmemberis further fitted with a manually operable lever for forcibly removing athroat plate to be fitted to the throat plate receiving seat.

i F l

1. A sewing machine including a frame having a bed with a worksupporting surface, a thread carrying eyed needle supported on the framefor endwise reciprocation, a needle thread take-up mechanism mounted onthe frame for alternately tightening and loosening the needle thread intimed relationship with the endwise reciprocation of the needle, saidbed having an opening formed with a throat plate receiving seat aboutsaid opening, a loop taker assembly mounted in the bed below the throatplate receiving seat and circularly moved for seizure of thread loopsformed by the reciprocation of the needle to form lock stitches, amechanism for linearly feeding a work fabric including a feed dog makingthe known four motions to advance the work fabric in a prescribeddirection on the work supporting surface during each endwisereciprocation of the needle, a movable loop retaining member positionedin the opening of the bed for temporarily retaining the loop which isbeing pulled up by the thread take-up mechanism following the releasefrom the loop taker assembly, an urging means connected to the loopretaining member for normally setting the loop retaining member in aposition to retain the loop released from the loop taker assembly, andan actuating member provided between the loop retaining member, and thefeed dog and having a first portion operatively connected with the loopretaining member, a second portion disposed adjacent the opening of thebed and a third portion normally urged toward the lower end of the feeddog, said actuating member being adapted to move the loop retainingmember against the action of the urging means by the downward movementof the feed dog, thereby causing the loop retained by the loop retainingmember to be released therefrom after the needle passes through the loopin the next downward movement, said second portion of said actuatingmember being adapted to be engaged by an actuating means on the bottomof a throat plate to thereby hold the loop retaining member in thereleased position for lock stitching.
 2. A sewing machine according toclaim 1 including a throat plate formed with an actuating means on theunderside thereof engaging the second portion of the actuating memberthereby disengaging the actuating member from the feed dog and settingthe loop retaining member in non-operable condition.
 3. A sewing machineaccording to claim 1 including a throat plate and a thread quantityadjusting means, said thread quantity adjusting means being provided forreducing the quantiTy of the needle thread slackened by the threadtake-up mechanism in co-operation therewith, said thread quantityadjusting means including an actuatable member adjacent said opening insaid bed, and an actuating projection formed on the underside of saidthroat plate cooperating with said actuatable member for bringing thethread quantity adjusting means in an operable position so as to reducethe quantity of the needle thread.
 4. A sewing machine according toclaim 3 wherein said thread take-up mechanism includes a reciprocablethread take-up lever, and said thread quantity adjusting member is bentin U-shaped to pass the take-up lever therein.
 5. A sewing machineaccording to claim 1 wherein said feeding mechanism includes means forcausing the feed dog to remain in its lowered position and an operatingknob for the same, thereby the loop retaining member is brought inarresting condition not to retain the loop released from the loop takerassembly through the actuating member when the operating knob isoperated.
 6. A sewing machine including a frame having a bed with a worksupporting surface, a thread carrying eyed needle supported on the framefor endwise reciprocation, a needle thread take-up mechanism mounted onthe frame for alternately tightening and loosening the needle thread intime relationship with the endwise reciprocation of the needle, said bedhaving an opening formed with a throat plate receiving seat about saidopening, a throat plate removably mounted on the throat plate receivingseat about said opening to close the opening of the bed, and perforatedwith a needle aperture adapted for chain stitching, a loop taker mountedin the bed below the throat plate and rotated about an axis for seizureof thread loops formed by the reciprocation of the needle to form lockstitches, a bobbin case retainer journaled in the loop taker and adaptedto accomodate an ordinary bobbin case therein, a restraining memberfixed in the bed below the throat plate for preventing the bobbin caseretainer from rotating with the loop taker, a mechanism for linearlyfeeding a work fabric including a feed dog making the known four motionsto advance the work fabric in a predetermined direction during eachendwise reciprocation of the needle, a loop retaining member rotatblysupported on the restraining member to temporarily retain the loop whichis being pulled up by the thread take-up mechanism following the releasefrom the loop taker at one of its end, spring means stretched betweenthe loop retaining member and the restraining member for imparting arotating force to the loop retaining member to normally keep it in aposition to retain the loop released from the loop taker, an actuatingplate having a base end swingably supported by the restrain member, anintermediate portion disposed adjacent the opening of the bed and a freeend normally urged toward the lower end of the feed dog by theengagement of the other end of the loop retaining member to which arotating force is imparted by the spring means, said actuating platebeing adapted to swing downward by the downward movement of the feed dogto rotate the loop retaining member against the action of the springmeans, thereby causing the loop retained by the loop retaining member tobe released therefrom after the needle passes through the loop in thenext downward movement.
 7. A sewing machine according to claim 6 whereinthe restraining member is further fitted with a manually operable leverfor forcibly removing a throat plate to be fitted to the throat platereceiving seat.